The utility of phentolamine, an alpha adrenergic blocking agent, as a myocardial protective agent is being studied. The model for study is one of global ischemia and reperfusion. The animal for study is the genetic strain of spontaneously hypertensive rats. The preparation is a combination of the original isolated heart apparatus as defined by Langendorff and the working leff atrial perfusion modification of Neely. The data generated at this point have shown that phentolamine ameliorates the deleterious effects of global ischemia. This effect was observed at 38 degrees centigrade and at 25 degrees centigrade. Additionally, salutory effects were observed when the drug was given at the onset of ischemia or at the initiation of re-perfusion.